CN103972648A - Antenna direct modulation system based on polarization refactoring - Google Patents

Abstract

The invention discloses a direct antenna modulation system based on polarization reconstruction for broadband communication, which mainly solves the problems of narrow communication bandwidth and poor confidentiality in traditional modulation systems. The modulation system includes: a ring slot antenna, a communication control circuit and a dielectric substrate. The ring slot antenna includes a feed network and a radiator, and the radiator consists of a radiation ring (6) and two rectangular slots (8), and the two rectangular slots are respectively located at 45° and 225° of the radiation ring; the feed network It consists of a microstrip feeder (3) and a slot line (4). The radiator and the slot line are located on the same side of the dielectric substrate, and the microstrip feeder is located on the other side of the dielectric substrate. Through the microstrip feeder (3) and the slot line (4) The coupling of the carrier signal is input to the radiator, and the polarization control of the electromagnetic field radiated by the antenna is realized through the on and off of the communication control circuit, forming a direct modulation effect based on polarization switching. The invention has good communication effects of frequency bandwidth and direction confidentiality, and can be used for broadband communication.

Description

Direct Antenna Modulation System Based on Polarization Reconstruction

technical field

The invention belongs to the technical field of antennas, and in particular relates to an antenna modulation system which can be used for broadband communication.

Background technique

As shown in Figure 2, the traditional communication method is to first load the modulated signal containing the transmission information on the carrier signal through amplitude modulation, phase modulation, frequency modulation, etc. to form a radio frequency signal with a certain bandwidth; then the radio frequency signal is amplified by power , shifting and equal processing, it is fed to the antenna through the transmission line, and then radiated out through the antenna. The bandwidth of the RF signal determines the bandwidth of the communication. Since the radio frequency signal is transmitted and radiated in multiple stages, the bandwidth of the communication system is composed of the intersection of the bandwidth of the radio frequency power amplifier, shifter and other components, and the bandwidth of the antenna feed structure, antenna matching network, and antenna radiation structure. If the communication bandwidth is narrow, the communication capacity will be greatly limited. In addition, because the signal difference in each radiation direction of the traditional communication method is only manifested as the difference in radiation intensity, it is easier to be intercepted and eavesdropped by a high-sensitivity receiver.

Direct Antenna Modulation (DAM, Direct Antenna Modulation) was first proposed by Fusco and Chen in 1999, and in recent years, promoted by Steven D.Keller of Duke University and Babakhani of California Institute of Technology, the amplitude-based Unit direct modulation technology and phase-based array direct modulation technology.

The direct antenna modulation technology directly modulates the radiated signal at the antenna level, so it avoids the bandwidth limitations of the communication system imposed by the power amplifier, phase shifting, feed network, and matching network, and has the ability to form broadband communication. And it has been proved to have certain direction secrecy characteristics. There are currently two main direct modulation methods:

The first is direct modulation based on amplitude. This modulation method is to control the on-off situation between the antenna and the floor through the communication control circuit to realize two states of antenna working and non-working, thereby realizing amplitude modulation. Although the method is simple in structure, it has poor concealment and is easy to be identified;

The second is phase-based direct modulation. This modulation method usually achieves directional communication by controlling the phase of unit excitation in the array. Although this modulation method ensures directional confidentiality, the array structure is complex.

Contents of the invention

The purpose of the present invention is to provide a direct antenna modulation system based on polarization reconfiguration to solve the problems of simplifying the modulation structure and improving concealment at the same time.

To achieve the above object, the present invention includes: a ring slot antenna, a communication control circuit and a dielectric substrate, the ring slot antenna includes a radiator and a feed network, and the communication control circuit is used to control the radiation characteristics of the ring slot antenna; it is characterized in that:

The radiator consists of a radiation ring and two rectangular slots. The radius of the radiation ring is inversely proportional to the resonant frequency of the ring slot antenna. The two rectangular slots are respectively located at 45° and 225° of the radiation ring for Make the ring slot antenna exhibit circular polarization characteristics;

The feed network consists of a microstrip feeder and a slot line. The slot line is connected to the radiation ring. The carrier signal is transmitted to the radiation ring through the coupling structure of the microstrip feeder and the slot line, and radiated from the radiation ring.

Further, both ends of the 45° axis of the radiation ring are provided with inner and outer extension slots for connecting the communication control circuit, the inner extension slots are respectively located between the radiation ring and the two rectangular slots, and the extension slots are respectively located on the other side of the two rectangular slots. One end, and extends to the bottom of the 45° axis of the radiating ring.

Further, the communication control circuit includes a modulation signal source, a carrier frequency signal source, two diodes and two capacitors; the two diodes are respectively connected on both sides of the inner extension gap between the radiation ring and one end of the two rectangular slots; the two capacitors They are respectively connected to both sides of the extension slot at the other end of the two rectangular slots; the modulation signal source is connected to both sides of the bottom end of the extension slot; the carrier frequency signal source is connected to the input end of the feed network.

Further, the slot line and the radiator are located on the same surface of the dielectric substrate, the upper end of which is connected to the radiation ring, and the lower end is a circular slot for impedance matching of the slot line.

Further, the microstrip feeder is located on the other side of the dielectric substrate, which is composed of two microstrip feeders horizontally and vertically. The intersection of the two microstrip feeders is provided with a 45° cut angle, and the bottom end of the vertical line passes through the coaxial feeder head Connect with the output terminal of the carrier frequency signal source.

The direct antenna modulation system based on polarization reconstruction provided by the present invention uses the carrier signal to excite the radiation ring through the microstrip feeder-slot line coupling feed structure to form carrier radiation; The slot forms a perturbation of the phase of the radiation current, and at the same time, a diode is connected across the gap between the slot and the radiation ring, and the perturbation of the phase is changed through the conduction and cut-off of the diode, forming linear polarization, left-handed circular polarization/right-handed circular polarization of the radiation field The circular polarization can be reconfigured; the modulation signal is added to the diode to form a direct modulation effect based on polarization switching, which realizes a broadband communication effect much higher than that of the traditional mixing communication method.

The present invention has the following advantages:

(1) Since the present invention adopts a radiator structure composed of a radiation ring and two rectangular slots, its working state can be changed through the communication control circuit, that is, when the diode in the communication control circuit is cut off, the rectangular slot and the radiation ring When the diode is turned on, the antenna radiation field is circularly polarized. When the diode is turned on, the rectangular slot and the radiation ring are disconnected. At this time, the antenna radiation field is linearly polarized; through this switching and control of the polarization, direct modulation is realized. The structure is simple and easy to implement; at the same time, due to the use of this radiator structure composed of a radiation ring and two rectangular slots, the circular polarization effect in the vertical direction of the antenna center can be the best. As the viewing direction leaves this direction, the circular polarization axis The ratio becomes worse, and gradually tends to linear polarization, and the switching and modulation effects become worse, so as to realize the direction secrecy.

(2) Since the present invention adopts a direct modulation method, only a single-frequency point carrier signal needs to be transmitted through the feed network, so the entire feed network does not need to be designed for broadband, and impedance matching can be easily realized.

(3) The present invention is not limited by the bandwidth of the antenna system because the antenna is directly modulated, and the information is transmitted by switching the line/circular polarization of the radiation field, and the broadband communication can be realized without carrying out broadband design to the antenna, greatly Reduced design difficulty.

The actual test results show that the present invention better solves the bandwidth problem of the existing communication system on the premise of ensuring a simple modulation structure, and is beneficial to secure communication.

Description of drawings

Fig. 1 is a schematic structural diagram of a direct modulation system based on polarization reconstruction in the present invention;

FIG. 2 is a schematic diagram of a traditional modulation method;

Fig. 3 is a schematic diagram of the direct modulation method of the present invention;

Fig. 4 is a surface current distribution diagram under the antenna working line polarization situation in the present invention;

Fig. 5 is the distribution diagram of the surface current in the case of circular polarization in which the antenna works in the present invention;

Fig. 6 is a graph comparing test results of radiation signal spectrum formed by the direct modulation method of the present invention and the traditional modulation method.

Specific implementation

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Referring to Fig. 1, the present invention includes a ring slot antenna, a communication control circuit and a dielectric substrate 14, wherein:

The dielectric substrate 14 is a double-sided copper clad laminate, one side of which is a conductive substrate 5 and the other side is a microstrip feeder 3 .

Referring to Fig. 1(a), the loop slot antenna includes a feeding network and a radiator. The radiator consists of a radiation ring 6 and two rectangular slots 8 . The radiation ring 6 is located at the geometric center of the conductive substrate 5, and its radius is inversely proportional to the working frequency of the ring slot antenna. Two rectangular slots 8 are located at 45° and 225° of the radiation ring 6 respectively, and the length and width of the rectangular slots 8 are inversely proportional to the circular polarization working frequency. The feed network is composed of microstrip feeder 3 and slot line 4 . The microstrip feeder 3 is composed of two microstrip feeders horizontally and vertically. In order to reduce the energy loss of the signal at the corner, an isosceles right triangle whose side length is the width of the microstrip feeder is cut off at the corner, that is, a 45° cut angle is formed; The upper end of the slot line 4 is connected to the radiation ring 6, and the lower end is a circular slot for impedance matching of the feed system. The widths of the microstrip feeder 3 and the slot line 4 both meet their characteristic impedance of 50Ω, so as to achieve the best coupling effect.

The communication control circuit is composed of two capacitors 7, two diodes 9, an extension slot 10, an extension slot 11, a modulation signal source 13 and a carrier frequency signal source 1; the extension slot 11 is respectively located between the radiation ring 6 and the two Between the two rectangular slots 8 , the extension slits 10 are respectively located at the other ends of the two rectangular slots 8 , and extend to the bottom of the 45° axis of the radial ring 6 . The conductive substrate 5 is divided into upper left and lower right parts along the 45° axis by the radiation ring 6, two rectangular grooves 8, extension slits 10 and inner extension slits 11; two diodes 9 are respectively connected between the radiation ring 6 and the lower right. Two capacitors 7 are respectively connected to both sides of the extension gap 10 at the other end of the two rectangular slots 8 on both sides of the inner extension gap 11 between one ends of the two rectangular slots 8 . The modulation signal source 13 is connected to both sides of the bottom end of the epitaxial slot 10 , and the modulation signal is applied to both ends of the two diodes 9 through the connection line 12 . The carrier frequency signal source 1 is connected to the input end of the feed network, and the carrier signal is transmitted to the microstrip feeder 3 through the coaxial feed head 2 .

The slot line 4, the radiation ring 6, two capacitors 7, the rectangular slot 8, two diodes 9, the extension slit 10, and the extension slit 11 are located on the same side of the dielectric substrate 14, that is, one side of the conductive substrate 5, such as As shown in Fig. 1(a), the microstrip feeder 3 is located on the other side of the dielectric substrate, as shown in Fig. 1(b).

With reference to Fig. 3, the modulation step of the present invention is as follows:

Step 1, the carrier signal is transmitted through the radio frequency circuit, antenna feed and matching network, and finally radiated through the antenna.

The carrier signal source 1 transmits the carrier signal to the microstrip feeder 3 through the coaxial feed joint 2 , and then feeds the carrier signal through the slot line 4 into the radiation ring 6 to form electromagnetic carrier radiation.

In step 2, the transmission signal modulates the antenna, and the communication is realized by transmitting information through the change of the radiation field of the antenna during the modulation process.

The modulation signal source 13 applies the modulation voltage to both ends of the two diodes 9. When the signal of the modulation signal source 13 changes, the two diodes 9 will switch between on and off, and at the same time, the electromagnetic wave radiated by the radiation ring 6 will be on-line Switch between polarization and circular polarization to realize antenna modulation.

Based on the above modulation steps, the working principle of the antenna in the present invention is as follows:

The electromagnetic carrier radiation passes through the rectangular slots 8 introduced at the 45° and 225° positions of the radiation ring 6 , which disturbs the current phase on both sides of the radiation ring 6 , thereby forming a circularly polarized radiation field. When the two diodes 9 are turned on, the surface current of the antenna is shown in Figure 4. It can be seen that since the rectangular slot is disconnected from the radiation slit, there is almost no influence on the current, and the current distribution at this time is close to the surface current of a typical annular slot antenna distribution, forming a linearly polarized electromagnetic radiation field on both sides perpendicular to the antenna surface; when the two diodes 9 are cut off, the rectangular slot communicates with the radiation gap, and the current on the antenna surface is shown in Figure 5. It can be seen that the rectangular slot generates Obviously, the current distribution changes, and a left-handed circularly polarized radiation field is formed on the side perpendicular to the antenna surface, and a right-handed circularly polarized radiation field is formed on the other side.

In order to control the on and off of the diode, the epitaxial slit 10 and the internal extension slit 11 divide the conductive substrate 5 into two parts, the upper left and the lower right, and realize the connection between the two parts of the conductive substrate 5 through the capacitor 7 at the same time. Carrier signal connection and modulation signal isolation. Due to the conduction of the substrate 5, the voltage of the modulation signal source 13 is applied to the diode 9. When the signal of the modulation signal source 13 changes, the diode 9 switches between on and off, and at the same time switches the electromagnetic field radiated by the radiation ring 6 between linear polarization and circular polarization, realizing direct modulation.

The present invention can realize the characteristics of broadband and confidential communication under the premise of ensuring a concise structure, and these two characteristics can be further explained through actual measurement and theoretical analysis.

1. Broadband test

With antenna among the present invention as transmitting antenna, in the traditional modulation mode shown in Fig. 2 and the direct modulation system of the present invention shown in Fig. 3 respectively, change modulation signal frequency, test its radiation field spectrum, carrier signal is 2.04 in the test GHz, compare the communication bandwidth of these two modulation methods, the results are shown in Figure 6. in:

Figure 6(a) is the radiation field spectrum obtained by the traditional communication method shown in Figure 2 when the modulation signal is 100MHz;

Fig. 6 (b) is when modulating signal is 100MHz, uses the radiation field spectrum that the direct modulation mode of the present invention as shown in Fig. 3 obtains;

Figure 6(c) is the radiation field spectrum obtained by the traditional communication method shown in Figure 2 when the modulation signal is 300MHz;

Fig. 6(d) is the radiation field spectrum obtained by using the direct modulation method of the present invention as shown in Fig. 3 when the modulating signal is 300 MHz.

As can be seen from the comparison of Fig. 6(a) and Fig. 6(b), at 100MHz, both can obtain frequency components of 2.04±0.1GHz and 2.04±0.2GHz, but the direct modulation antenna of the present invention can also The frequency components of 2.04±0.3GHz and 2.04±0.4GHz are obtained, reflecting the broadband characteristics of the latter.

From the comparison of Figure 6(c) and Figure 6(d), it can be seen that when the modulation signal increases to 300MHz, the 2.04±0.3GHz spectrum signal corresponding to the radiation field of the traditional communication method is already very small, which does not meet the communication requirements. However, the direct modulation antenna of the present invention can still obtain clear 2.04±0.3GHz spectrum signals, and this phenomenon is still valid when the modulation signal is increased to 400MHz. The reason for this experimental result is that the communication bandwidth of the direct modulation system is not limited by the radio frequency circuit, antenna feed and matching network, or even the antenna bandwidth, but only depends on the rate of direct modulation of the antenna. The rate of this direct modulation depends on the diode response speed. Therefore, compared with traditional communication, direct antenna modulation can realize broadband communication.

2. Confidentiality analysis

When the antenna of the embodiment of the present invention works in the circular polarization state, it only presents a good circular polarization effect in the direction perpendicular to the antenna. As the observation direction leaves this direction, the ratio of the circular polarization axis becomes worse and gradually tends to the line polarization. But this is precisely what constitutes directional secrecy. This is because: since the transmission of information relies on the switching of polarization, the modulation effect corresponding to the switching of linear polarization and circular polarization in the vertical direction of the antenna is obvious, while in other directions as the characteristics of circular polarization become worse, this Switching the modulation effect will be worse. This makes the bit error rate of the communication in the vertical direction of the antenna lower than that in other directions, forming a secure communication with directional selectivity.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For example, the present invention implements modulation based on polarization control, and other embodiments may also include all direct antenna modulation based on polarization switching, such as based on Direct antenna modulation based on the switching of two mutually orthogonal linear polarizations and the switching of left-handed and right-handed circular polarizations. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. the direct antenna modulating system based on polarization reconstruct, comprises ring slot antenna, communication control circuit and medium substrate, and circumferential weld gap antenna comprises radiant body and feeding network, and communication control circuit is for the radiation characteristic of control ring slot antenna; It is characterized in that:

Radiant body, formed by radiation annulus (6) and two rectangular channels (8), the radius of this radiation annulus (6) is inversely proportional to the resonance frequency of ring slot antenna, these two rectangular channels (8) lay respectively at 45 ° and 225 ° of radiation annulus (6) and locate, and present circular polarization characteristics for making to encircle slot antenna;

Feeding network, formed by microstrip feed line (3) and the line of rabbet joint (4), the line of rabbet joint (4) is connected with radiation annulus (6), carrier signal is delivered to radiation annulus (6) by the coupled structure of microstrip feed line (3) and the line of rabbet joint (4), and radiate from radiation annulus (6).

2. the direct antenna modulating system based on polarization reconstruct as claimed in claim 1, it is characterized in that, 45 ° of axis two ends of radiation annulus (6) be provided with extension gap (10) and in prolong gap (11), for connecting control circuit.

As claimed in claim 2 based on polarization reconstruct direct antenna modulating system, in it is characterized in that, prolonging gap (11) lays respectively between radiation annulus (6) and two rectangular channels (8), extension gap (10) lays respectively at the other end of two rectangular channels (8), and reaches 45 ° of axis bottoms of radiation annulus (6) always.

4. the direct antenna modulating system based on polarization reconstruct as claimed in claim 1 or 2, it is characterized in that communication control circuit, comprise modulating signal source (13), CF signal source (1), two diodes (9) and two electric capacity (7); Two diodes (9) be connected between radiation annulus (6) and two rectangular channels (8) one end in prolong both sides, gap (11); Two electric capacity (7) are connected to the both sides, extension gap (10) of two rectangular channels (8) other end; Modulating signal source (13) is connected to the both sides, bottom in extension gap (10); CF signal source (1) is connected to the input of feeding network.

5. the direct antenna modulating system based on polarization reconstruct as claimed in claim 1, it is characterized in that the line of rabbet joint (4) and radiant body are positioned at the same face of medium substrate (14), its upper end is connected with radiation annulus (6), lower end is a circular recess, for the line of rabbet joint is carried out to impedance matching.

6. the direct antenna modulating system based on polarization reconstruct as claimed in claim 1, it is characterized in that microstrip feed line (3) is positioned at the another side of medium substrate (14), it is by two microstrip-fed compositions anyhow, these two microstrip-fed intersections are provided with 45 ° of corner cuts, and vertical line bottom is connected with the output in CF signal source by coaxial feed joint.

7. the direct antenna modulating system based on polarization reconstruct as claimed in claim 5, it is 50 Ω that the width that it is characterized in that microstrip feed line (3) and the line of rabbet joint (4) all meets its characteristic impedance, to reach Best Coupling effect.